Bone anchoring device with spherical articulation

ABSTRACT

The invention concerns a bone anchoring device comprising a bone anchoring element provided with a head for receiving a threaded shaft whereon a clamping means is designed to be screwed, a spherical articulation being provided between the bone anchoring element and the threaded shaft to provide the threaded shaft with multiple orientation. The invention is characterized in that it comprises means for rotational linkage between the bone anchoring element and the threaded shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of International Patent ApplicationNo. PCT/FR2003/002167, filed Jul. 10, 2003, which claims priority toFrench Patent Application No. 02/08 838 filed Jul. 12, 2002, thedisclosure of which is hereby incorporated herein in its entirety byreference.

FIELD OF THE INVENTION

The present invention relates to the technical field of osteosynthesisnotably of the vertebral column and more specifically it is directed toan anchoring device in vertebrae, used in osteosynthesis systems for thevertebral column.

More specifically, the object of the invention is directed to a boneanchoring device, such as an anchoring screw in order to have a relativeangulation with an osteosynthesis system implementing a linkage rod forexample.

BACKGROUND OF THE INVENTION

One of the known applications of the object of the invention relates tosystems designed for correcting and stabilizing the vertebral column andfor facilitating bone fusion at different levels of the vertebralcolumn. According to such an application, such a system includes anintervertebral linkage element such as a rod or a plate able to be bentand positioned along the vertebral column while being held in positionby screws implanted in the vertebrae in order to follow the curvature ofthe region of the fitted-out vertebral column. Hence, in order to complywith the anatomy of the vertebral column, the linkage rod should beconformed in order to have large angulations notably for its mountingrelatively to the lumbar and sacral vertebrae.

In order to allow such conformations of the rod while ensuring itseffective locking relatively to the anchoring screws, fitting out theanchoring screws with a spherical articulation for receiving the linkagerod is known for allowing an adaptive relative angulation between theanchoring screw and the intervertebral linkage element.

SUMMARY OF THE INVENTION

Many anchoring devices of the spherical articulation type have beenproposed in the state of the art. Thus, a bone anchoring device isknown, which includes a bone anchoring element such as a screw providedwith a head for receiving a threaded shaft whereon a clamping means of alinkage rod is designed to be screwed. A spherical articulation isprovided between the bone anchoring element and the threaded shaft so asto provide the threaded shaft with multiple orientations. According toan exemplary embodiment, the end of the threaded shaft includes meansfor receiving an ancillary allowing rotational locking of the threadedshaft during the operation for screwing or unscrewing of the clampingnut on the threaded shaft. It thus appears that the operation forscrewing or unscrewing the nut on the threaded shaft is an operationrequiring the use of different ancillaries, which complicates andlengthens the operation for placing an osteosynthesis system.

A bone anchoring device is also known from U.S. Pat. No. 5,628,740,including a bone anchoring element provided with a head for receiving athreaded shaft whereon a clamping means is designed to be screwed. Aspherical articulation is provided between the bone anchoring elementand the threaded shaft. The threaded shaft includes two diametricallyopposite studs engaging with grooves provided in the head fitting thebone anchoring element. Theses studs cooperate with grooves to allow thepivoting of the threaded shaft.

Multiple orientation of the threaded shaft relatively to the boneanchoring element cannot be maintained with such a device, whileproviding effective rotational linkage, between the bone anchoringelement and the threaded shaft.

The object of the invention is therefore directed to remedy thedrawbacks of the prior art by proposing a bone anchoring device withwhich screwing or even unscrewing of a clamping nut on the threadedshaft may be provided simply and securely, otherwise maintaining itsmultiple orientation function for the threaded shaft.

To achieve such goals, the bone anchoring device according to theinvention includes a bone anchoring element provided with a head forreceiving a threaded shaft upon which a clamping means is designed to bescrewed, a spherical articulation being provided between the boneanchoring element and the threaded shaft to allow for multipleorientation of the threaded shaft. According to the invention, the boneanchoring device includes rotational linkage means between the boneanchoring element and the threaded shaft, while maintaining multipleorientation of the threaded shaft relatively to the bone anchoringelement.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the invention, reference is made to thefollowing detailed description, taken in connection with theaccompanying drawings illustrating various embodiments of the presentinvention, in which

FIG. 1 is schematic view of an exemplary embodiment of a bone anchoringdevice according to the invention;

FIG. 2 is an elevation sectional view at a larger scale of the exemplaryembodiment illustrated in FIG. 1;

FIG. 3 is a partial perspective view showing a characteristic feature ofthe object of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout, and prime notation is used toindicate similar elements in alternate embodiments.

As it is apparent in the figures, the object of the invention relates toa bone anchoring device 1 intended to be implanted in the vertebralcolumn. Such a bone anchoring device 1 includes a bone anchoring element2, broadly speaking, suitable for being made in different known ways.The bone anchoring element 1 may exist as a hook, a plate or ananchoring screw such as illustrated in the drawings. This bone anchoringelement 2 is provided with a head 3 for receiving a threaded shaft 4whereon a clamping means 5 is designed to be screwed. Conventionally, aspherical articulation 6 is provided between the bone anchoring element2 and the threaded shaft 4 in order to allow multiple orientation of thethreaded shaft 4 relatively to the bone anchoring element 2.

In the illustrated exemplary embodiment, the threaded shaft 4 at theopposite end of its free end, is provided with a ball-and-socket joint 7of hemispherical shape mounted on the inside of a housing 8 with acomplementary shape in order to form the spherical articulation 6. Inthe illustrated example, the housing 8 is provided inside the receivinghead 3 which exists as a grip nut for a screwing tool. This receivinghead 3 which, for example, is reported as being fixed on the boneanchoring element 2, includes an aperture 9 opening into the housing 8in order to allow the passage of the threaded shaft 4 and its multipleorientation angular displacement relatively to the bone anchoringelement 2. Of course, provision may be made for making theball-and-socket joint 7 on the end of the bone anchoring element 2 andthe housing 8 on the threaded shaft 4.

According to the invention, the bone anchoring device 1 includesrotational linkage means 10 between the bone anchoring element 2 and thethreaded shaft 4. In other words, the bone anchoring element 2 and thethreaded shaft 4 are directly linked in rotation while maintainingmultiple orientation for the threaded shaft 4 relatively to the boneanchoring element 2. In this respect, the linkage means 10 are madeoutside the spherical articulation 6.

As it is more specifically apparent from FIGS. 2 and 3, the rotationallinkage means 10 consist of a geometrical form or female imprint 11cooperating with a complementary geometrical form or male imprint 12.One of the geometrical forms 11, 12 is provided on the receiving head 3of the bone anchoring element 2 whereas the other geometrical form ismade on the end of the threaded shaft 4.

These female 11 and male 12 geometrical forms are said to becomplementary in the sense that a rotational force exerted along theaxis of the bone anchoring element 2 or of the threaded shaft 4 leads torotational locking between the bone anchoring element 2 and the threadedshaft 4, regardless of the relative orientation between these two parts.Such rotational locking is directly obtained between the bone anchoringelement 2 and the threaded shaft 4 without the help of other parts. Itshould therefore be contemplated that the female 11 and male 12geometrical forms may have transverse cross-sections with identical ordifferent shapes. In the illustrated exemplary embodiment and asapparent from FIG. 3, the transverse cross-sections of the female 11 andmale 12 geometrical forms are substantially rectangular. Of course, thefemale 11 and male 12 geometrical forms may have sections with differentshapes, such as elliptical, oval, non-circular shapes with at least oneedge, etc. The female geometrical form 11 is provided by a cavity orhousing whereas the male geometrical form 12 is achieved by a stud or aprotruding portion.

As it is apparent from the above, the female 11 and male 12 geometricalforms delimit clearance between them to allow multiple orientationbetween the threaded shaft 4 and the bone anchoring element 2 whileproviding rotational linkage between the male and female geometricalforms.

Preferably, it should be noted that the transverse face 14 delimitingthe ball-and-socket joint 7 and the end face 2 ₁ of the bone anchoringelement 4 extend, facing each other and at a distance from one another,in order to allow multiple orientation of the threaded shaft 4.Advantageously, the transverse face 14 of the ball-and-socket joint 7and/or the end face 2 ₁ of the bone anchoring element 2 have a convexshape in order to allow such an orientation with limited bulkiness.

One of the geometrical forms, i.e., the male geometrical form 12 in theillustrated example is provided on the end of the bone anchoring element2 whereas the female geometrical form 11 is provided at the free end ofthe threaded shaft 4. More specifically, the female geometrical form 11is made in the transverse face 14 delimiting the hemisphericalball-and-socket joint 7, whereas the male geometrical shape 12 is madeon the end face 2 ₁ of the bone anchoring element 2. Of course, theposition of the male and female geometrical forms on the threaded shaftand on the bone anchoring element may be reversed.

The anchoring device 1 according to the invention therefore has aspherical articulation thereby allowing an adaptive relative angulationbetween the bone anchoring element 2 and a member of an osteosynthesissystem such as a linkage rod. The fixing of this linkage rod via aclamping means 5 is achieved in a simple way without having to resort toan ancillary to hold the threaded shaft 4 in position in so far as thelatter may not rotate because of the anchoring of element 2 and of thepresence of the rotational linkage means 10.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims.

1. A bone anchoring device comprising: a bone anchoring element providedwith a head for receiving a threaded shaft upon which a clamping meansis screwed; a spherical articulation being provided between the boneanchoring element and the threaded shaft in order to allow multipleorientation of the threaded shaft; and rotational linkage means betweenthe bone anchoring element and the threaded shaft for maintainingmultiple orientation for the threaded shaft relatively to the boneanchoring element.
 2. The bone anchoring device according to claim 1,wherein the rotation linkage means are provided outside the sphericalarticulation.
 3. The bone anchoring device according to claim 1, whereinthe rotational linkage means includes a female geometrical formcooperating with a complementary male geometrical form, delimitingbetween them clearance in order to allow multiple orientation betweenthe threaded shaft and the bone anchoring element.
 4. The bone anchoringdevice according to claim 3, wherein one of the geometrical forms isprovided on the head of the bone anchoring element, and wherein theother geometrical form is provided on the end of the threaded shaft. 5.The bone anchoring device according to claim 3, wherein one of thegeometrical shapes is provided on an end face of the bone anchoringelement, extending within an open housing provided in the head andreceiving the end of the threaded shaft made as a ball-and-socket jointin order to form the spherical articulation, said ball-and-socket jointbeing provided with the other geometrical form on its transverse face.6. The bone anchoring device according to claim 5, wherein thetransverse face of the ball-and-socket joint and the end face of thebone anchoring element extend a distance from one another in order toallow multiple orientation of the threaded shaft.
 7. The bone anchoringdevice according to claim 6, wherein at least one of the transverse faceof the ball-and-socket joint and the end face of the bone anchoringelement has a convex shape.
 8. The bone anchoring device according toclaim 5, wherein the male geometrical form is made on the end of thebone anchoring element, and wherein the female geometrical form isprovided on the ball-and-socket joint.
 9. The bone anchoring deviceaccording to claim 1, wherein the receiving head forms a grip nut for ascrewing tool.